Liquid membrane process for the separation of aqueous mixtures

ABSTRACT

This invention relates to a process for the removal of dissolved species from aqueous solutions, which comprises contacting said aqueous solution with an emulsion, said emulsion comprising an exterior phase which is characterized as being immiscible with said aqueous solution and yet permeable to said dissolved species, and an interior phase which contains a reactant capable of converting said dissolved species to a non-permeable form. The dissolved species permeate the exterior phase, into the interior phase where they are converted into nonpermeable forms and thus retained in the interior phase of said emulsion. The aqueous solution, depleted in said dissolved species, is separated from said emulsion and the emulsion cycled for reuse. In one preferred embodiment said dissolved species are ions, and an ion exchange compound is incorporated in the exterior phase of the emulsion, to promote the permeation of said ions through the exterior phase.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. Nos.28,094 and .Badd..[.99,267.]. .Baddend..Iadd.36,686 .Iaddend.filed onApr. 13, 1970 and .[.Dec. 17, 1970.]. .Iadd.May 12, 1970.Iaddend.respectively, in the names of Li, Cahn and Shrier. ApplicationSer. No. 28,094 has issued as U.S. Pat. No. 3,617,546, and applicationSer. No. .Badd..[.99,267.]..Baddend. .Iadd.36,686 .Iaddend.has issued asU.S. Pat. No. .Badd..[.3,710,519.]..Baddend. .Iadd.3,637,488. .Iaddend.

BACKGROUND OF THE INVENTION

This invention relates to a process for the removal of dissolved species(solute) from aqueous solutions, which comprises contacting said aqueoussolution with an emulsion, said emulsion comprising an exterior phasewhich is characterized as being immiscible with said aqueous solutionand yet permeable to said dissolved species, and an interior phase whichcontains a reactant capable of converting said dissolved species to anon-permeable form. The dissolved species permeate the exterior phase,into the interior phase where they are converted into non-permeableforms and thus retained in the interior phase of said emulsion. Theaqueous solution, depleted in said dissolved species, is separated fromsaid emulsion and the emulsion cycled for reuse. In one preferredembodiment said dissolved species are ions, and an ion exchange compoundis incorporated in the exterior phase of the emulsion, to promote thepermeation of said ions through the exterior phase.

Liquid surfactant membranes, as disclosed in U.S. Pat. No. 3,454,489,may be utilized to separate dissolved compounds from their aqeuoussolutions. The process described therein is based on diffusion throughthe liquid surfactant membrane, and thus the limit of separation wasreached when the concentration of the dissolved compounds on both sidesof the membrane became equal.

It has now been unexpectedly discovered that a dissolved species may beefficiently removed from an aqueous solution by contacting said aqueoussolution with an emulsion, said emulsion comprising an exterior phasewhich is immiscible with said aqueous solution and permeable to saiddissolved species, and an interior phase comprising a reactant which iscapable of converting said dissolved species to a form in which it is nolonger permeable. The dissolved species in its non-permeable form isthus trapped in the interior phase and the concentration gradient of thepermeable form of said compound between the aqueous solution and theinterior phase is maintained. The concentration gradient acts to drivethe dissolved compound efficiently through the exterior phase of theemulsion into the interior phase. By use of this technique small volumesof emulsion may be used to treat large volumes of aqueous solutionefficiently. Thus the instant process, although not limited thereto, isuseful in water pollution control, wherein large bodies of water must betreated to remove small amounts of dissolved impurities, e.g., thedissolved species.

The exterior phase of the emulsion will comprise one or moresurfactants, a solvent, if needed, and/or various other additives, asfurther elucidated below. The exterior phase is designed to beimmiscible with said aqueous solution, and to form an effectiveemulsion, must also be immiscible with the interior phase and with thereactant in the interior phase. The exterior phase acts as a liquidmembrane through which selected, dissolved species may permeate into theinterior phase where they are converted to nonpermeable forms.

The dissolved species which may be removed by the instant processinclude inorganic and organic, neutral and ionic, acidic and basiccompounds. In each specific case the exterior phase of the emulsion mustbe chosen so that the dissolved species is at least slightly solubletherein. It will be obvious to the skilled artisan which exterior phasemay be used for any specific dissolved species. The exterior phase maybe specially adapted to solubilize any dissolved species by use of asolubilizing additive. For example, hydrocarbon soluble ion exchangecompound can be dissolved in a hydrocarbon exterior phase to promote thesolubility of ionic species therein.

The choice of reactant will be made in view of two factors. It must becapable of converting the dissolved species, e.g., compound, which haspermeated into the interior phase, into a nonpermeable form, thustrapping said dissolved compound and keeping the concentration of saidcompound low in the interior phase. Also, said reactant must itselfremain trapped in the interior phase. Usually the reactant will besoluble in the interior phase, but the use of insoluble reactants, i.e.,solid adsorbents, or slightly soluble reagents like lime in an aqueousinterior phase is feasible.

In a typical example of how the instant process may be utilized, a waterimmiscible solvent containing a surfactant soluble therein, is mixedwith an aqueous solution containing a reactant under high shearconditions to form a stable water in oil emulsion. Said emulsion is thencontacted with an aqueous stream containing a dissolved species by anyof various methods, i.e., agitating a mixture of the emulsion and theaqueous stream together in a batch process, cocurrent containing in acontinuous flow reactor; countercurrent contacting by bubbling saidaqueous stream through a column containing said emulsion, or vice versa.In all of these procedures a difference in density between said aqueousstream and said emulsion is maintained in order to permit separation ofthe emulsion and the aqueous stream after contact.

During contact, the dissolved species present in the aqueous streampermeates through the exterior phase of the water in oil emulsion, intothe interior phase, which comprises the reactant-containing solution,wherein said dissolved species reacts with said reactant and isconverted into a nonpermeable form (thus keeping the concentration ofthe permeable form low in the interior phase). If the reactant was notpresent, the dissolved species would continue to permeate into theinterior phase until the concentration of said dissolved species in theinterior phase was equal to its concentration in the aqueous stream. Atthis point further permeation into the interior phase would cease.

By providing a reactant capable of converting said permeable speciesinto a nonpermeable form, in the interior phase, the concentration ofthe permeable form of the dissolved species in the interior phase isheld below the concentration in the aqueous stream. The dissolvedspecies is thus continuously forced into the interior phase by theresulting concentration gradient.

The various dissolved species which may be separated from their aqueoussolutions include weakly basic compounds, e.g., NH₃, various amines, andother nitrogen-containing organic compounds. In general these arereacted in the interior phase with a strong acid, e.g., H₂ SO₄, HCl,HNO₃, which neutralizes said basic compounds and converts them into anionic, i.e., nonpermeable form. By maintaining a pH difference betweenthe aqueous solution and the interior phase, the concentration of thepermeable, un-ionized form of said compounds can be maintained high inthe aqueous stream and low in the interior phase.

Weakly acidic compounds, e.g., CO₂, SO₂, acetic acid, H₂ S, phenol, HCN,citric acid and many other organic acids are reacted in the interiorphase with a strong base, e.g., NaOH, K₂ CO₃, KOH and are converted toionic i.e., nonpermeable forms.

Various dissolved species may be precipitated in the interior phase, andthus converted to a nonpermeable form. Examples include the removal ofH₂ S by reaction with copper ions, and the removal of HCN by reactionwith silver ions, said ions being dissolved in the interior phase.

Ionic species may also be separated from their aqueous solutions by useof the instant process, the only proviso being that said ionic speciesbe at least somewhat soluble in the water immiscible exterior phase ofthe emulsion.

For example, ions of tin, iron and copper, being slightly soluble inaromatic and olefinic solvents, may be separated from aqueous solution,by utilizing a water in oil emulsion comprising an aromatic or olefinicsolvent as the exterior phase.

Generally, various solubilizing additives, i.e., compounds which aresoluble in the water immiscible exterior phase and are capable ofinteraction with ions to solubilize them, are added for the promotion ofthe permeation of ions through the exterior phase.

If it is desirable to remove cations from an aqueous solution, acompound selected from the group consisting of sulfonic acids, organophosphoric acids, and carboxylic acids, may be incorporated in theexterior phase. It should be noted that compounds chosen from this groupmay also function as surfactants. However, best results, i.e., balancingthe emulsion stability with the rate of transfer of ions across themembrane, are obtained when a nonionic surfactant as hereinafterdescribed is combined with one of these compounds.

In general, when removing cations from an aqueous solution, the waterimmiscible exterior phase will comprise a non-ionic surfactant and acompound selected from the group consisting of polyfunctional sulfonicacids, polyfunctional carboxylic acids, and polyfunctional organophosphoric acids said polyfunctional compounds are known in the art asion exchange compounds. Said ion exchange compounds generally have amolecular weight of from 200 to 10,000 and will have a ratio of carbonatoms to functional group of greater then 5.

Examples of ion exchange compounds which are useful for transfer of ionsthrough the membrane include: sulfonated styrene copolymers, petroleumsulfonic acids, naphthenic acids, sulfonated phenol formaldehydecopolymers, styrene-maleic acid copolymers, styrene-acrylic acidcopolymers, etc.

When it is desirable to remove anions, then amines may be incorporatedin the exterior phase. Amines may, likewise, function as surfactants,but as previously noted, the best balance of emulsion stability and iontransfer, requires a non-ionic surfactant and an amine.

The useful amines are also known in the art as ion exchange compoundsand will contain more than 4 carbon atoms per nitrogen atom.

Useful amines include styrene copolymers containing pendant quaternaryammonium groups, including derivatives of trimethylamine ordimethylethanolamine.

A preferred group of amines are compounds of the general formula##STR1## wherein R and R₁ are independently selected from the groupconsisting of hydrogen, C₁ to C₂₀ alkyl, C₆ to C₂₀ aryl and C₇ to C₂₀alkaryl radicals and R₂ is selected from the group consisting of C₆ toC₃₀ alkyl, C₆ to C₂₀ aryl and C₇ to C₂₀ alkaryl radicals. Specificexamples within the above definition include di-n-decylamine,dilaurylamine, methyldioctylamine, tri-n-octylamine, tri-iso-octylamine,tribenzylamine, tri-p-butylbenzylamine, tricaprylamine,1-amino-1,1,3,3,5,5,7,7,9,9-decamethyl decane (Primene JM-T)didodecenyl-n-butylamine, trilaurylamine, etc.

Most preferred compounds, within the above definition are Primene JM-Tand Amberlite LA- 2 a N-lauryl trialkyl methylamine, both available fromRohm and Haas Co.

Various polyamine derivatives are useful within the scope of the instantinvention. The preferred polyamine derivatives are those having thegeneral formula: ##STR2## wherein R₃, R₄, [R₅, R₆, R₇, R₈, R₉ and y] arechosen from the group consisting of hydrogen, C₁ to C₂₀ alkyl, C₆ to C₂₀aryl, C₇ to C₂₀ alkaryl radicals and substituted derivatives thereof;and x is an integer of from 1 to 100. More preferably R₅, R₆, R₇, R₈,and R₉ are hydrogen, and x varies from 3 to 20.

The substituted derivatives previously mentioned are preferably selectedfrom the group consisting of oxygen, nitrogen, sulfur, phosphorous, andhalogen containing derivatives.

In the most preferred polyamine derivative, R₃ and R₄ together form analkyl succinic radical having the general formula ##STR3## wherein nvaries from 10 to 60, x varies from 3 to 10, R₅, R₆, R₇, R₈ and R₉ arehydrogen, and y is selected from the group consisting of hydrogen andoxygen-containing hydrocarbyl radicals having up to 10 carbons e.g.,acetyl, etc.

Once the ions permeate into the interior phase, they may be convertedinto a nonpermeable form by precipitation, complexing, etc. with areactant maintained in the interior phase. Examples of such conversionsinclude precipitation of Ag, Cu, Cd, and Hg ions with sulfide ions;precipitation of Ca ions with phosphate ions and vice versa; reductionof nitrate ions with ferrous ions and complexing of nitrogen oxide withferric sulfate. Any of the well known ion complexing agents such asethylene diamine tetra acetic acid may be utilized as reactants.

An interesting variation of the above process for separating ions fromaqueous solution involves maintenance of a pH differential between theinterior phase and the aqueous solution, whereby the pH at the aqueoussolution-exterior phase interface promotes the solubility of the ions inthe ion exchange compound containing exterior phase, and the pH at theexterior phase-interior phase interface promotes the desorption of theions from the exterior phase and subsequent solubilizing in the interiorphase.

The process of this invention contemplates the separation of dissolvedcompounds from aqueous solution, and thus [in order to maintain theemulsion as a phase separate from said aqueous solution] it is necessarythat the emulsion be of the water in oil type. The surfactants utilizedwill be of the oil soluble type. In general the surfactants must havelow solubility in both the aqueous solution and the interior phase.Also, the surfactant preferably promotes the permeability of thedissolved species of interest through the membrane. Specific surfactantswhich may be used include anionic, cationic, or nonionic surfactants.

The following anionic surfactants are useful for the process of theinstant invention:

Carboxylic acids, including fatty acids, rosin acids, tall oil acids,branched alkanoic acids, etc.

Sulfuric acid esters, including alcohol sulfates, olefin sulfates, etc.

Alkane and alkylaryl sulphonates, including alkyl benzene sulfonates,alkyl naphthalene sulphonates, etc.

Phosphoric acid esters, including mono and dialkyl phosphates.

The following cationic surfactants are useful for the process of theinstant invention:

Quaternary amine salts.

Nonionic surfactants are the preferred surfactant type for the practiceof the process of the instant invention. A useful group of nonionicsurfactants include the polyethenoxyether derivatives of alkyl phenols,alkylmercaptans, and alcohols, e.g. sorbitol, pentaerythritol, etc.

Particular nonionic surfactants for use in the instant process includecompounds having the general formula ##STR4## wherein R₁₀ may be C₈ H₁₇,C₉ H₁₉, or C₁₀ H₂₁ and m is an integer varying from 1.5 to 8.

The most preferred nonionic surfactant is Span 80, a fatty acid ester ofanhydro sorbitol condensed with ethylene oxide.

Short-chain fluorocarbons with polar groups are frequently sufficientlysoluble in hydrocarbon oils to function as surfactants. Long-chainfluorocarbons attached to a hydrocarbon chain of sufficient length aresoluble in hydrocarbon oils.

Silicone oils differ broadly in their chemical structure andsurface-active properties. Those of sufficiently low molecular weight tobe soluble in the hydrocarbon solvent and which contain only CH₃ groupsattached to silicon in the (Si--O)_(n) skeleton can be expected to besurface-active.

Since the number of surfactants is extremely large, it is not intendedto burden this application with numerous examples. The followingpublications may be referred to for further examples: Surface Chemistryby Lloyd I. Osipow, Reinhold Publishing Company, New York (1962) chapter8 and Surface Activity, Moilliet et al, Van Nostrand Company, Inc.(1961) Part III.

Generally the exterior phase of the emulsion comprises a waterimmiscible solvent, as well as one or more surfactants. The solvent maybe chosen from the class consisting of hydrocarbons, halogenatedhydrocarbons, ethers, higher oxygenated compounds such as alcohols,ketones, acids and esters.

The various additives which have been previously mentioned as useful fortransporting ions across the membrane may function as the waterimmiscible solvent. In particular the various amines previouslymentioned are useful solvents for the formation of water in oilemulsions.

The solvent, of course, must be liquid at the conditions at which theinstant process is operated, and also must be capable, in conjunctionwith the surfactant, of forming a stable water in oil emulsion with theinterior phase. Conveniently the interior phase is aqueous but anysolvent which forms and maintains the interior phase of a stableemulsion with the selected surfactant-solvent exterior phase mixture maybe used.

The interior phase exists as droplets surrounded by thesolvent-surfactant exterior phase. When the water in oil emulsion iscontacted with the aqueous solution, the exterior phase acts as a liquidmembrane which allows certain dissolved species to permeate into theinterior phase where a reactant contained therein converts them to aform which cannot permeate back through the "liquid membrane."

The water in oil emulsion must be stable so that the exterior phasecoating the droplets of the interior phase does not rupture and thusallow mixing of the components of the interior phase with the aqueoussolution.

It should be noted that a variation of the above process is possiblewherein the aqueous solution comprises the interior phase of the waterin oil emulsion, which is then contacted with a solution containing areactant for the dissolved species. This variation although possible isnot economically favored for treating pollution, where large volumes ofaqueous solution would have to be emulsified, but may be of interestwhere small streams must be treated with large volumes of reactant.

The emulsion used in the instant process may be prepared by variousmethods. Weight ratios of from 0.1 to 1.8, preferably of from 0.5 to1.0, of a reactant solution is mixed with a water immiscible solvent inwhich is dissolved at least about 0.0001 percent by weight, preferablyfrom about 0.01 percent by weight to 10 percent by weight, mostpreferably from 0.1 percent by weight to 5 percent by weight of an oilsoluble surfactant. The reactant solution is preferably aqueous with aconcentration that is dependent primarily on the solubility of thereagent in the aqueous solution. Preferably the aqueous solution issaturated with the reactant or may be a slurry containing undissolvedreactant. The above mixture is emulsified by use of high speed stirrers,colloid mills, valve homogenizers, ultrasonic generators or mixing jets.

When an ion exchange compound is incorporated in the exterior phase ofthe water in oil emulsion, it may comprise from about 1 to 99.9 percentby weight of said exterior phase. Preferably said ion exchange compoundwill comprise from about 4 to about 40 percent by weight of saidexterior phase.

A typical water in oil emulsion, for use in separating ions from aqueoussolutions, will thus comprise from 0.01 to 10 percent by weight nonionicsurfactant, from 5 to 75 percent by weight ion exchange compound, andfrom 25 to 75 percent by weight of an aqueous solution containing areactant for the aforesaid ion.

The emulsion is then contacted with an aqueous solution containingdissolved compounds, in a manner as previously described, whereby thedissolved compounds permeate through the "liquid membrane" exteriorphase into the reagent-containing interior phase, wherein said dissolvedcompounds are converted to nonpermeable forms. The emulsion is thenseparated from the aqueous solution, which is now depleted in thedissolved compounds, and optionally the emulsion is cycled to a recoveryarea, where it may be regenerated. For example, the emulsion may bebroken, the surfactants and solvent reused for making fresh emulsion,and the reactant regenerated for reuse.

The above process may be operated at any temperature at which theemulsion and the aqueous solution are fluid and stable; conveniently,ambient temperature is used. The pressure must likewise be sufficient tomaintain the fluidity of various phases; conveniently, ambient pressuresare used.

The following are specific embodiments of the instant process. The aboveprocess is general in scope, and thus there is no intention of beinglimited to said specific embodiments.

EXAMPLE 1

In the following runs, phenol was removed from an aqueous solution. Thesolution was introduced into a separation zone which was provided with amixer. The zone was maintained at a temperature of 25° C. and a pressureof 1 atmosphere. The surfactant used was Span 80, a commercial name forsorbitan monooleate with a viscosity of 1,000 cps at 25° C., in anamount of 2 percent by weight. The mixture of surfactant, sodiumhydroxide solution and surfactant solvent (a high molecular weightisoparaffin having a carbon number range of from about 25 to about 35)was emulsified and then contacted with the phenol-containing aqueousfeed. After the emulsion and the aqueous solution were mixed at a rateof 100 rpm for about 50 minutes, the emulsion and the aqueous solutionwere separated and analyzed. The results and additional details of theexperiments are included in Table I. The aqueous solution was analyzedby UV spectrography method for phenol concentration and by titrationwith acid for caustic concentration.

The Table indicates that in Run 1 where no sodium hydroxide was added, ahigh phenol concentration remained after 43 minutes of agitation. On theother hand, in Run 2 where 0.4 wt. percent of caustic was used, at theend of 19 minutes only 3 parts per million of phenol remained. In Run 3where the caustic concentration was increased slightly to 0.5 wt.percent, phenol was reduced from 1,000 to 33 parts per million in just53 minutes.

It should be noted that the Na content of the waste water rose veryslowly, indicating very little permeation of Na-ion from the "inside" ofthe emulsion to the outside waste water stream.

EXAMPLE 2

In this example phosphoric acid and mono sodium phosphate were removedfrom aqueous solutions. The aqueous solution of phosphate was introducedinto a separation zone which was provided with a mixer. The zone wasmaintained at ambient temperature and pressure. The surfactant used wasSpan 80. The mixture of emulsion containing surfactant, calciumcompounds, surfactant solvents, high molecular weight amines withmolecular weight below 1,000, and the phosphate-containing aqueous feedwas stirred at a rate of 100 rpm for about 50 minutes. The results andadditional details of the experiments are included in Table II. The feedrecovered was analyzed by colorimetric method for phosphateconcentration and by titration method for chloride concentration whencalcium chloride was used.

                  Table I                                                         ______________________________________                                        EXPERIMENTAL PHENOL REMOVAL                                                   FROM WASTE STREAMS                                                                           Run number                                                                    1      2        3                                              ______________________________________                                        Aqueous phenol solution:                                                       Ce              250      250      250.                                        Phenol, p.p.m   1,000    200      1,000.                                     Emulsion:                                                                      Exterior phase  Iso-     Iso-     Iso-                                                        paraffin paraffin paraffin.                                   Volume of exterior phase, cc                                                                  200      200      200.                                        Surfactant      2%       2%       2%                                                          Span 80  Span 80  Span 80.                                    Interior aqueous phase, cc                                                                    100      96.8     97.                                         Caustic conc., wt. percent                                                                    0        0.4      0.5.                                       ______________________________________                                    

    __________________________________________________________________________    RUN DATA                                                                          Phenol in      Phenol in      Phenol in                                       aqueous        aqueous        aqueous                                     Time,                                                                             solution,                                                                           Percent                                                                            Time,                                                                             solution,                                                                           Percent                                                                            Time,                                                                             solution,                                                                           Percent                               min.                                                                              p.p.m.                                                                              removed                                                                            min.                                                                              p.p.m..sup.1                                                                        removed                                                                            min.                                                                              p.p.m..sup.2                                                                        removed                               __________________________________________________________________________    0   990   0    0   200   0    0   1,000 0                                     2   730   26   1   83    59   2   652   35                                    5   667   33   2   60    70   5   288   71                                    8   615   38   3   36    82   18   41   96                                    28  606   39   5   17    92   38   44   96                                    43  612   38   19  3     98   53   33   97                                    __________________________________________________________________________     .sup.1 No NaOH in aqueous phase                                               .sup.2 Na in final aqueous phase=43 p.p.m.                               

The example is representative of using an ion exchange compound topromote the permeation of ionic compounds through the exterior emulsionphase, and the subsequent conversion to a nonpermeable form byprecipitation with reagent.

The Table indicates that in Runs 2 and 5 where there were no calciumcompounds inside the droplets, a high phosphate concentration remainedafter 44 minutes of agitation. Although the membranes themselves didremove some phosphate, such process is highly inefficient and thereforenot economical. On the other hand in Run 1 where 6.0 wt. percent ofcalcium chloride was used, at the end of 18 minutes only 0.05 percent ofphosphate remained. In the other experiments where 15 percent CaCl₂ and5 percent Ca(OH)₂ where used, phosphate was reduced from 0.273 percentto 0.004 percent in 44 minutes in Run 3 and from 0.273 percent to 0.018percent in 44 minutes in Run 4.

It should be noted that the Cl content of the waste water rose veryslowly, indicating slow permeation of Cl-ion from the "inside" of theemulsion to the outside waste water stream.

                                      TABLE II                                    __________________________________________________________________________    EXPERIMENTAL PHOSPHATE REMOVAL FROM WASTE WATER                                           Run number                                                                     1              2       3                4    5                   __________________________________________________________________________    (1)                                                                             Aqueous feed (gm.)                                                                      107                    500                                        (2)                                                                             Phosphoric                                                                              NaH.sub.2 PO.sub.4 . H.sub.2 O                                                                       NaH.sub.2 PO.sub.4 . H.sub.2 O +                                              H.sub.3 PO.sub.4                             compound                         (1:1 by wt.).                              (3)                                                                             Emulsion used(gm.)                                                                      97                     281                                        (4)                                                                             Surfactant solvent                                                                      49% JMT primene plus 49%                                                                             95% isoparaffin (see Example 1);                       polyamine derivative..sup.a                                                                          Amberlite LA-2.sup.b plus 2%                                           (1) to (7)                                                                           polyamine derivative..sup.a                                                                     (1) to                                                                             (1) to (7)          (5)                                                                             Wt. percent organic                                                                     66.9            are same                                                                             67                are                                                                                are same              surfactant solution       as Run 1.                as Run                                                                             as Run 3.             in emulsion.                                                                (6)                                                                             Surfactant                                                                              2% Span 80             1% Span 80                                 (7)                                                                             Wt. percent aqueous                                                                     33.1                   33                                           phase in emulsion.                                                          (8)                                                                             Reagents (wt. per-                                                                      6% CaCl.sub.2 + 6%                                                                            None   15% CaCl.sub.2 + 5% Ca(OH).sub.2                                                                     None                  cent in aq. phase).                                                                     NH.sub.4 OH (0.1 N)                                               __________________________________________________________________________

    __________________________________________________________________________    (9) RUN DATA                                                                  Time,  PO.sub.4.sup.-3 (wt.                                                                Cl.sup.-  (wt.                                                                     PO.sub.4.sup.-3 (wt.                                                                PO.sub.4.sup.-3 (wt.                                                                Cl.sup.-1 (wt.                                                                     PO.sub.4.sup.-3 (wt.                                                                PO.sub.4.sup.-1 (wt.)                min.   percent)                                                                            percent)                                                                           percent)                                                                            percent)                                                                            percent)                                                                           percent)                                                                            percent                              __________________________________________________________________________    Feed                                                                             0   0.565 0    0.565 0.273 0    0.273                                         2   0.265 0.084                                                                              0.338 0.123 0.036                                                                              0.133 0.204                                   5   0.200 0.0168                                                                             0.314 0.073 0.065                                                                              0.120 0.205                                   18  0.050 0.0110                                                                             0.316 0.016      0.075 0.206                                   44             0.204 0.004 0.103                                                                              0.108 0.204                                __________________________________________________________________________     ##STR5##                                                                      m is an integer of about 40, giving said polyamine derivative a molecular     weight of about 2,000.                                                        .sup.b Amberlite LA-2 is a trade name for high molecular weight (mol. wt.     353-393) primary and secondary amines which are oil-soluble but not           water-soluble, have anion exchange resin properties, possess a                neutralization equivalent of 360-380, an ion exchange capacity of 2.7         meq./gm., a viscosity of 18 cps. at 25° C. and a density of 0.83       gm./ml.                                                                  

EXAMPLE 3--Separation of nitrate.

279 gm of liquid membrane emulsion are mixed with 465 gm of an aqueousnitrate solution at 200 RPM. The emulsion was made by emulsifying 100 gmreagent solution composed of 50 percent H₂ SO₄, 20 percent Fe SO₄, and30 percent H₂ O in 200 gm surfactant solution (2 percent Span 80 and 98percent isoparaffin [See Example 1]). The aqueous solution contained219.3 ppm of NaNO₃ in water. After the feed and the emulsion werecontacted for 2 minutes, the concentration of NaNO₃ in the feed droppedto 35.64 ppm. The concentration only increased slightly to 41.12 ppmafter continuous mixing for 53 minutes more, thus indicating that therewas very little membrane rupture during the mixing period.

A blank run was made in which 282 gm of liquid membrane emulsion wasmixed with 492 gm. feed. The emulsion, containing no reagent, was madeby emulsifying 100 gm pure water in 200 gm of the same surfactantsolution. The same aqueous solution was used in the run. After theaqueous nitrate solution was continuously mixed with the emulsion for 68minutes the concentration of NaNO₃ was only reduced from 219.3 ppm to205.6 ppm, indicating the removal of the nitrate in the absence ofreagent was insignificant.

EXAMPLE 4-- Separation of Ammonia

Aqueous solution: Water containing NH₄ OH (690 ppm)

Surfactant solution= 2 percent Span 80+ 98 percent isoparaffin (seeExample 1) 200 gm.

Reagent solution= 2 percent HCl in water-- 100 gm.

Mixed 237 gm. of the water in oil emulsion with 500 gm feed at 250 RPM.Samples were taken from time to time from the aqueous solution.

    ______________________________________                                                          NH.sub.4 OH Concentration                                                     in                                                          Mixing time       Aqueous solution                                            (Min)             (ppm)                                                       ______________________________________                                        0                 690                                                         2                 250                                                         5                 130                                                         18                <30                                                         38                <30                                                         53                <30                                                         Total Time of                                                                 mixing = 53 minutes.                                                          ______________________________________                                    

What is claimed is:
 1. A process for removal of a dissolved species froman aqueous solution which comprises, contacting said aqueous solutionwith an emulsion, said emulsion comprising an interior phase, surroundedby a surfactant containing exterior phase, said exterior phase beingimmiscible with said aqueous solution and said exterior phase beingpermeable to said dissolved species, and said interior phase comprisinga reactant capable of converting said species to a nonpermeable species,whereby said species permeates the exterior phase and is converted to anonpermeable species in the interior phase.
 2. The process of claim I,wherein said exterior phase comprises from about 0.01 to 10 weightpercent of an oil soluble surfactant.
 3. The process of claim 2 whereinsaid interior phase is aqueous.
 4. The process of claim 3 wherein saiddissolved species is converted to a nonpermeable form by complexing witha reactant in the interior phase.
 5. The process of claim 3 wherein saiddissolved species is an ion.
 6. The process of claim 5 wherein saidexterior phase comprises an ion exchange compound.
 7. The process ofclaim 6 wherein said ion is a cation.
 8. The process of claim 7 whereinsaid exterior phase comprises a compound selected from the groupconsisting of sulfonic acids, organophosphoric acids and carboxylicacids.
 9. The process of claim 6 wherein said ion is an anion.
 10. Theprocess of claim 9 wherein said exterior phase comprises an amine. 11.The process of claim 3 wherein said dissolved species is converted to anonpermeable form in the interior phase by neutralization.
 12. Theprocess of claim 11 wherein said dissolved species is a weak acid and isneutralized in the interior phase by a strong base.
 13. The process ofclaim 12 wherein said weak acid is selected from the group consisting ofCO₂, SO₂, acetic acid, H₂ S, phenol, HCN and citric acid.
 14. Theprocess of claim 11 wherein said dissolved species is a weak base and isneutralized in the interior phase by a strong acid.
 15. The process ofclaim 14 wherein said dissolved species is selected from the groupconsisting of NH₃ and nitrogen containing organic compounds.
 16. Theprocess of claim 3 wherein said dissolved species is converted to anonpermeable form by precipitating in the interior phase.
 17. Theprocess of claim 16 wherein said dissolved species is selected from thegroup consisting of metal ions.
 18. The process of claim 17 wherein saidmetal ion is selected from the group consisting of Ag, Cu, Cd and Hg.19. The process of claim 3 wherein said surfactant is Span
 80. 20. Theprocess of claim 7 wherein said ion exchange compound is selected fromthe group consisting of sulfonated styrene copolymers, petroleumsulfonic acids, napthenic acids, sulfonated phenol formaldehydecopolymers, styrene-maleic acid copolymers, and styrene acrylic acidcopolymers.
 21. The process of claim 9 wherein said ion exchangecompound is selected from compounds having the general formula: ##STR6##wherein R and R₁ are independently selected from the group consisting ofhydrogen, C₁ to C₂₀ alkyl, C₆ to C₂₀ aryl and C₇ to C₂₀ alkaryl radicalsand R₂ is selected from the group consisting of C₆ to C₃₀ alkyl, C₆ toC₂₀ aryl and C₇ to C₂₀ alkaryl radicals; and ##STR7## wherein R₃, R₄,R₅, R₆, R₇, R₈, R₉ and y are independently selected from the groupconsisting of hydrogen, C₁ to C₂₀ alkyl, C₆ to C₂₀ aryl, C₇ and C₂₀alkaryl radicals and substituted derivatives thereof, and x is aninteger of from 1 to
 100. 22. The process of claim 21 wherein R₃ and R₄together form an alkyl succinic radical having the general formula##STR8## wherein m is an integer varying from 10 to 60, x varies from 3to 10, and y is selected from the group consisting of hydrogen andoxygen containing hydrocarbyl radicals having up to 10 carbons.